FR2855137A1 - Hydraulic braking equipment for vehicle, has simulator with cylinder having bore containing electrorheological fluid whose viscosity increases with stroke and speed of movement of brake pedal - Google Patents

Abstract

The equipment has a simulator (M) comprising a cylinder with a bore (17) in which a head of a piston (18) slides. The bore has electrorheological fluid whose viscosity depends on electrical field to which it is subjected. Connections apply a high voltage that depends on stroke of a brake pedal (9), between the piston and the cylinder. The viscosity of the fluid increases with stroke and speed of movement of the brake pedal. The piston is subjected to a brake fluid pressure on one side and an opposition force on another side. The head includes grooves constituting a reduced sectional passage between the piston and the bore for permitting a braked fluid flow during movement of the piston in the bore.

Description

BRAKING SYSTEM EQUIPPED WITH A SIMULATOR FOR

  VEHICLE, AND SIMULATOR FOR SUCH AN INSTALLATION.

  The invention relates to a hydraulic braking installation for a vehicle, of the type which includes, for actuating wheel brakes - a service braking system with external energy; - a muscular energy emergency braking system; a manual control member, the advance of which actuates the service braking system or, in the event of the latter failing, the emergency braking; - a master cylinder with at least one piston, the displacement of which is ensured by the manual control member; at least one safety valve making it possible either to isolate the master cylinder from the wheel brakes when the service braking 15 is operating normally, or, in the event of a service braking failure, to connect the master cylinder to at least one wheel brake; a braking sensation simulator for opposing the advance of the manual control member, during an external energy service braking, a reaction reflecting the progress of the braking, this simulator 20 comprising a cylinder in which can slide a simulator piston subjected on one side to a pressure of brake fluid coming from the master cylinder and, on the opposite side, to an opposing force.

  A braking system of this type is known, for example from FR-2,772,706.

  In such an installation, during normal operation in service braking mode, the master cylinder is isolated from the wheel brakes and the liquid contained in the master cylinder cannot flow back to the brakes.

  Thanks to the sensation simulator which allows a transfer of the brake fluid, the manual control member, for example brake pedal, maintains a normal actuation stroke, dependent on the force exerted.

  The known installations give relatively satisfaction by making it possible to create a law of variation of the force to be exerted on the manual control member, as a function of the stroke, which gives the user a sensation similar to that which would be obtained if the Fluid pressure in the wheel brakes was a direct result of pressure from the master cylinder and muscle effort on the brake pedal.

  However, in most known installations, the law of variation of the force to be exerted on the manual control member is determined mainly by an elastic return means, generally formed by a spring, provided in the simulator and the law of variation cannot be changed quickly and easily.

  For various reasons, in particular depending on the type of car, it is desirable to be able to act on this law of variation in particular as a function of the travel and / or the speed of movement of the manual control member.

  For the same type of car, it may also be desirable to easily and quickly modify the law of variation of the opposing force, depending on the conditions of use of the car.

  The object of the invention is, above all, to provide a braking installation which better meets the various requirements mentioned above than hitherto and which, in particular, makes it possible to quickly and easily modify the law of variation of the force to be exerted on the manual control member as a function of the stroke and / or the speed of movement of this manual control member.

  According to the invention, a hydraulic braking installation for a vehicle, of the kind defined above, is characterized in that: the cylinder of the sensation simulator contains an electro-rheological liquid whose viscosity depends on the electric field to which it is subjected ; - A passage of reduced section is provided between piston and cylinder of the simulator to allow a braked flow during the displacement of the piston in the cylinder of the simulator; - And that electrical connection means are provided to apply between the piston and the cylinder of the simulator an electrical voltage which depends on the stroke of the manual control, the assembly being such that the viscosity of the electrorheological liquid increases with the stroke and / or the speed of movement of the manual control.

  Preferably, the simulator piston comprises a large diameter cylindrical head secured to a smaller diameter coaxial rod held and guided in sliding in a housing of corresponding diameter, the piston head sliding in a bore at a reduced distance from the wall. of the bore and without contact with this wall.

  The head of the simulator piston preferably has grooves on its cylindrical surface parallel to the generatrices, for the flow of electro-rheological liquid from one side to the other of the piston.

  The simulator piston is made of an electrically conductive metal, as is the wall of the bore surrounding the piston head, while the wall of the housing serving as a guide for the piston rod is electrically insulated from the wall of the bore containing the piston head, a high electrical voltage being applied to the piston rod and to the head, while the wall of the bore is earthed.

  The high electrical voltage, determining the electric field to which the electro-rheological liquid is subjected, is advantageously controlled by a computer which determines this voltage as a function of various parameters, in particular displacement and speed of displacement of the manual control member and liquid pressure at the outlet of the master cylinder.

  When the cylinder head has longitudinal grooves, an insulating layer of dielectric material may be provided around the outer surface of the piston head to slide against the wall of the bore.

  The service braking system generally comprises a pump, driven by motor means, capable of delivering liquid under a pressure depending on the stroke and / or the speed of movement of the manual control member, towards the brakes. wheels.

  The pressurized liquid discharged by the master cylinder is sent to the housing of the simulator piston rod and acts on the end of this rod.

  The delivery of the booster pump can be connected to the simulator cylinder on the side opposite the rod, while the chamber located on the rod side is connected to the wheel brake, so that the liquid pressure delivered by the pump is applied in the simulator cylinder on the side of the piston head opposite the rod. A bypass line can be provided to connect the pump outlet to the wheel brake.

  3.5 The service braking system pump is advantageously driven by a DC motor, the speed of which is controlled by a computer as a function of the stroke and / or of the speed of movement of the control member.

  The invention also relates to a braking sensation simulator capable of opposing in advance of a manual control member a reaction reflecting the progress of braking, this simulator 5 comprising a cylinder in which a piston can slide. simulator subjected on one side to a force depending on the pressure of the master cylinder and, on the opposite side, to an opposing force depending on the stroke and / or the speed of the control, characterized in that: - the cylinder the simulator contains an electro-rheological fluid 10 whose viscosity depends on the electric field to which it is subjected; - A passage of reduced section is provided between piston and cylinder to allow a braked flow of liquid; - And that electrical connection means are provided to allow to apply between piston and cylinder of the simulator an electrical voltage.

  The invention consists, apart from the arrangements set out above, in a certain number of other arrangements which will be more explicitly discussed below in connection with an exemplary embodiment described in detail with reference to the accompanying drawings, but which n is by no means limiting. In these drawings: Fig.1 is a simplified diagram of a braking installation for a vehicle according to the invention; Fig.2 is a perspective view with parts broken away of the simulator according to the invention; and Fig.3 is a partial section on a larger scale of the simulator.

  Referring to Fig. 1, a hydraulic braking installation 1 for a motor vehicle can be seen comprising a service braking system A supplied with pressurized liquid by a hydraulic power station 2 with external energy, and an emergency braking system B with muscular energy.

  The hydraulic unit 2 comprises a pump 3 driven by a motor 4, preferably an electric motor. The pump 3 supplies pressurized liquid to a main supply line 5. The suction of the pump 3 is connected by a line 6 to a reservoir 7 of pressureless liquid or tank. An EV3 two-position "open-closed" electrovalve is installed on line 6.

  The line 5 of liquid under pressure is connected in parallel, by respective lines such as 5a, to the wheel brakes such as 8a. An EV2 two-position "open / closed" solenoid valve is installed on each pipe such as 5a.

  The installation comprises a manual control member D, generally constituted by a brake pedal 9, and a master cylinder 10 in which a piston 11 can slide, or a primary piston and a secondary piston not detailed. The pedal 9 is linked to the piston 11 by a rod 12, one end of which is articulated on the pedal.

  The output of the master cylinder 10 is connected by a pipe 13 provided with a safety or stop solenoid valve EV1 to at least one wheel brake pipe Sa 8a. According to the example in FIG. 1, the connection 13 - Sa takes place via a simulator chamber M of the braking sensation described below.

  A sensor 14 for the travel of the pedal 9 is provided for sending an electrical signal representative of the displacement of the pedal to an input terminal of a computer C. The sensor 14 makes it possible to obtain information on the amplitude of the displacement pedal 9 as well as its speed of movement.

  A pressure sensor 15 is connected to the pipe 13 between the output of the master cylinder 10 and the electrovalve EV1 to supply an electrical signal representative of the output pressure of the master cylinder, sent to another input of the computer C. The brake actuation simulator M makes it possible to oppose in advance of the brake pedal 9 a reaction reflecting the progress of the braking when the latter is provided by the system A. The simulator M comprises a cylinder 16 with a bore 17 of relatively large diameter in which the head 18 of a piston 19 can slide, comprising a rod 20 coaxial with the head 18, but of smaller diameter.

  The rod 20 is guided in a cylindrical housing 21 secured to the body 16 of the simulator. The rod 20 slides in leaktight manner in this housing 21 by virtue of a seal 20a disposed in an annular groove in the rod. The end of the rod 20 remote from the head 18 defines a chamber 35 of variable volume connected by a pipe 23 directly to the outlet of the master cylinder 10.

  22 of variable volume connected by a pipe 23 directly to the outlet of the master cylinder 10.

  The housing 21 is produced in a part of the body 16 of the simulator which is electrically isolated from the rest of the body 16 by a layer I, schematically represented. A high electrical voltage HT can be applied to the rod 20 by an electrical connection 24 controlled by the computer C, while the remaining part of the simulator body 16, separated by the insulating layer I from the zone of the housing 21, is connected to the mass by a link 25.

  The guide of the rod 20 is provided so that the external cylindrical surface of the head 18 of the piston 19 remains at a distance from the surface of the bore 17 and determines an annular space h (FIG. 3) of reduced radial dimension. As a variant, an insulating layer may be provided on the wall of the bore 17 in order to allow the head 18 to be guided.

  The potential difference between the head 18, which is at the same high voltage HT as the rod 20, and the wall of the bore 17 connected to ground, creates an electric field with an essentially radial orientation in the space h. The equipotential lines, in a cross section, are constituted by circles such as E (Fig. 3) whose center is located on the geometric axis of the piston 19.

  The piston head 18 has on its cylindrical outer surface longitudinal grooves 26, of substantially rectangular cross section, parallel to the generatrices of the cylinder and regularly distributed over the entire periphery. The bore 17 is divided, by the head 18, into two chambers 27, 28. The chamber 27 is located on the side of the rod 20, the pipes 13 and 5a being connected to this chamber in the example of FIG. 1.

  The chamber 28 is located on the side of the head 18 opposite the rod 20. A return spring 29 is disposed in this chamber 28 between the head 18 and the bottom of the bore 17, electrical insulation being provided at least at the one of the ends of the spring 29 to maintain the potential difference between the head 18 and the body 16 of the simulator.

  The bore 17 of the simulator M contains an electrorheological liquid L whose viscosity depends on the electric field to which it is subjected. The viscosity of L is an increasing function of the electric field. 35 An example of an electro-rheological liquid corresponds to the reference LID 3354, having a density of 1460 kg.m The space h and the grooves 26 constitute a passage of reduced section between the head 18 of the piston and the bore 17 allowing a braked flow of the liquid L from one side of the head 18 to the other, during the displacement of the piston 19 in the bore 17.

  According to the alternative embodiment of Fig.1l, the entire braking installation 1 uses the electro-rheological liquid L stored in the tank 7.

  The main outlet line of the pump 3 is connected to the chamber 28 and, by a bypass 30, directly to the line 5a.

  The speed of rotation of the motor 4 driving the pump 3 is controlled by the computer C via an electrical connection 31 preferably according to a PMW command so that the speed of the motor 4 increases with the driving speed of the pedal 9, in order to ensure a faster increase of the braking force by the system A. Generally the braking installation is equipped with an ABS system (anti-lock of the wheels) which includes, for each brake wheel such as 8a an EV4 two-position "open / closed" solenoid valve disposed on a line 32 connecting the wheel brake 8a (downstream of the EV2 solenoid valve) to the suction of pump 3, via a non-return valve 33. A low pressure capacity 34 is connected to the pipe section between the EV4 solenoid valve and the valve 33.

  However, the operation of the braking system is as follows.

  When the service braking system A operates normally, as soon as the driver acts on the brake pedal 9, the electrovalve EV 1 closes, EV3 opens and the motor 4 is started so that the pump 3 delivers liquid under pressure. The EV2 solenoid valve is in the open position while EV4 remains in the closed position.

  The pressurized liquid discharged from the master cylinder 10 arrives, through line 23, into chamber 22 and acts on the end of the rod 20 of small section.

  The piston 19 therefore tends to move from right to left according to Fig.l. The advance resistance of the piston 19 is created by the braked flow of electro-rheological liquid L in the annular space 35 and in the grooves 26 of the piston head 18.

  This resistance to advancement of the piston 18, and therefore of the brake pedal 9, depends on the electric field applied between the surface of the piston 18 and the wall of the bore 17 which surrounds it. The law of variation of this electrical voltage HT as a function of depressing the pedal 9 is determined by the computer C, programmed for this purpose. The HV voltage increases with the degree of depressing of the pedal 9 and with the depressing speed of this pedal.

  According to the diagram in FIG. 1, a fraction of the flow rate of the pump 5 passes into the bore 17 and another fraction goes directly to the pipe 5a via the bypass line 30. The flow of liquid from the chamber 28 to the chamber 27 creates a force return on the piston 18 from the left to the right so that the return spring 29 may have reduced dimensions, as well as the cross section of the head 18 and the bore 17 in which it moves.

  In the case where the ABS system intervenes following a detection of a locking of a wheel, the opening of the valve EV4 is controlled by the computer of the ABS system and the capacity 34 begins to fill with liquid.

  According to an alternative embodiment, the bypass pipe 30 20 would be eliminated and all the flow of liquid coming from the pump 3 would pass through the grooves 26 and the space h between the head 18 and the bore 17.

  According to another variant, the outlet of the pump 3 would be connected only to the valve EV2 by the pipe 30, and isolated from the chamber 28. In such a variant, the return of the grooved piston 18 from the left to the right of FIG . It should be provided by the spring 29 alone which should therefore have larger dimensions. The cross section of the head 18 should also be greater to create sufficient resistance to depressing the pedal 9.

  Up to now, it has been considered that the liquid of the entire braking installation 30 is an electro-rheological liquid L. According to a variant, the presence of electro-rheological liquid could be limited to the simulator M whose bore 17 would not be no longer connected to lines 13 and 5a, nor to line 5. The simulator M, from the hydraulic point of view, would constitute an independent system containing the electro-rheological liquid in chambers 27 and 28. Line 13 would be connected directly to the pipe Sa while the outlet 5 of the pump 3 would be connected by line 30 to the pipe 5a. The brake system fluid would be a conventional hydraulic fluid which would act in chamber 22 while remaining separate from the electrorheological fluid in chambers 27 and 28.

  In the event of failure of the service braking system A, the computer C controls the opening of the solenoid valve EV1, and the emergency braking is ensured by the system B; the liquid pressure coming from the master cylinder 10 acts directly in the wheel brake 8a.

  Whatever the embodiment, the invention makes it possible to program 10 the modifications of the force / stroke law of the brake pedal 9 and to adapt this law according to the type of vehicle or even according to the driver. To do this, it suffices to act on the law of variation of the HV electric voltage programmed in the computer C, without having to modify the components of the braking installation. It is possible to allow the user to choose and / or modify the law of variation, within limits which would be fixed by construction.

Claims (12)

  1. Hydraulic braking installation for a vehicle comprising, for actuating wheel brakes: - a service braking system (A) with external energy; - an emergency braking system (B) with muscular energy; a manual control member (D), the advance of which actuates the service braking system (A) or, in the event of the latter failing, the emergency braking (B); - a master cylinder (10) with at least one piston (11) whose movement is ensured by the manual control member; - at least one safety valve (EV1) allowing either to isolate the master cylinder (10) from the wheel brakes (8a) when the service braking (A) 15 is operating normally, or, in the event of a service braking failure, connecting the master cylinder (10) to at least one wheel brake (8a); a braking sensation simulator (M) for opposing, in advance of the manual control member (D), during service braking with external energy, a reaction reflecting the progress of the braking, this simulator 20 comprising a cylinder (16) in which a simulator piston (19) can slide, subjected on one side to a pressure of brake fluid coming from the master cylinder and, on the opposite side, to an opposing force, characterized in that - the cylinder (16) of the sensation simulator contains an electro-rheological liquid (L) whose viscosity depends on the electric field to which it is subjected - a passage (h) of reduced section is provided between piston (19) and cylinder (16) of the simulator to allow braked flow when the piston moves in the simulator cylinder; - And that electrical connection means (24, 25) are provided for applying between the piston (19) and the cylinder (16) of the simulator an electric voltage (HT) which depends on the stroke of the manual control, the assembly being such that the viscosity of the electro-rheological liquid increases with the stroke and / or the speed of movement of the manual control (D).   2. Braking installation according to claim 1, characterized in that the piston (19) of the simulator comprises a cylindrical head (18) of large diameter secured to a coaxial rod (20) of smaller diameter maintained and guided in sliding in a housing (21) of corresponding diameter, the head (18) of the piston sliding in a bore (17) at a reduced distance from the wall of the bore and without contact with this wall.   3. Braking installation according to claim 2, characterized in that the head (18) of the simulator piston has on its cylindrical surface grooves (26) parallel to the generatrices.   4. Braking installation according to claim 2 or 3, characterized in that the piston (19) of the simulator is made of an electrically conductive metal, as well as the wall of the bore (17) surrounding the head of the piston, while the wall of the housing (21), serving as a guide for the rod (20) of the piston, is electrically insulated (I) from the wall of the bore 15 containing the head of the piston, a high electric voltage being applied to the piston rod (20) and to the head (18), while the wall of the bore is connected to ground.   5. Braking installation according to one of the preceding claims, characterized in that the electric voltage (HT), determining the electric field to which the electro-rheological liquid (L) is subjected, is controlled by a computer (C) which determines this voltage according to various parameters, according to a determined program.   6. Braking installation according to claim 5, characterized in that the electric voltage (HT) is controlled by the computer (C) as a function of the movement and of the speed of movement of the manual control member (D), and the liquid pressure at the outlet of the master cylinder (10).   7. Braking installation according to one of claims 2 to 4, characterized in that the pressurized liquid discharged by the master cylinder (10) is sent into the housing (21) of the rod (20) of the piston simulator and acts on the end of this rod.   8. Braking installation according to one of the preceding claims in which the service braking system (A) comprises a pump (3) capable of delivering liquid under a pressure depending on the stroke and / or the speed of movement. from the manual control member, to the wheel brakes, characterized in that the pump (3) is driven by a direct current motor (4) whose speed is controlled by a computer (C) depending on the stroke and / or the speed of movement of the control member (D).   9. Braking installation according to claims 2 and 8, characterized in that the discharge of the pump (3) is connected to the simulator cylinder (16) on the side opposite to the rod (20), while the cylinder chamber (22) located on the side of the rod is connected to the wheel brake (8a).   10. Braking installation according to claim 8 or 9, characterized in that a line (30) connects the outlet of the pump (3) to the wheel brake (8a).   11. A braking sensation simulator capable of opposing the reaction of a manual control member (D) a reaction reflecting the progress of braking, this simulator comprising a cylinder (16) in which a piston ( 19) subjected on one side to a force dependent on the pressure of a master cylinder (10) and, on the opposite side, to an opposing force dependent on the stroke and / or the speed of the control, characterized by fact that: - the cylinder (16) of the simulator contains an electro-rheological fluid (L) whose viscosity depends on the electric field to which it is subjected; - a passage of reduced section (h) is provided between piston and cylinder to allow a braked flow of liquid; - And that electrical connection means (24, 25) are provided to allow the application of an electric voltage (HT) between the piston and the cylinder of the simulator.   12. braking sensation simulator according to claim 11, characterized in that the piston (19) of the simulator comprises a cylindrical head (18) of large diameter secured to a coaxial rod (20) of smaller diameter maintained and guided in sliding in a housing (21) of corresponding diameter, the head (18) of the piston sliding in a bore (17) at a reduced distance from the wall of the bore and without contact with this wall, and comprising on its cylindrical surface grooves (26) parallel to the generators.